The present invention relates to a butterfly valve with a housing, a flow channel passing through the housing and a disk-shaped valve flap swivellable by a rotatably-mounted shaft closing the flow channel, the housing being subdivided into two parts along a separation plane at right angles to the flow channel having in each case an outwardly projecting flange, having a surface directed towards the separation plane and an outer surface directed away therefrom, recesses being provided in the vicinity of the separation plane for a seal surrounding the flow channel and the shaft.
A butterfly valve of this type is described in U.S. Pat. No. 4,060,220. The construction of its housing from stamped sheet parts, i.e. sheet metal halves machine formed by other than chip-producing processes with only slight chip-forming remachining, permits manufacture in material and labour-saving manner. The two housing halves, between which are guided and fixed in recesses the flap shaft and the seal sealing the housing halves against one another and also the flap shaft and the valve flap, have outwardly projecting flanges which are fastened together by a plurality of bolts. The provision of bolts requires a relatively large flange diameter, so that the screws are accessible for assembly and disassembly. To prevent deformations of the flange housing, it is necessary to provide numerous screws on the circumference, particularly if the housing is thin, which may be done for constructional reasons.
German Utility Model No. 7,916,836 discloses a butterfly valve, whose housing comprises two solid halves made from cast material or produced by chip-forming machining, whose separation plane passes through the rotational symmetry axis of the connection piece forming the flow channel. The sealing ring is supported on projections of the connection piece and on the housing. The housing also guides the flap shaft and is pressed together on either side by screws. This valve construction is very advantageous when manufactured from easily cast or chip-machined materials, such as e.g. aluminium, but involves very high material and labour costs in the case of materials such as stainless steel. Machining must also take place very precisely, because the two housing parts are engaged in the separation plane and determine the compression of the seal both directly and indirectly by the pressing together of the two connection pieces via sloping surfaces.
In addition, Offenlungungsschrift No. 2,810,683 discloses a butterfly valve of the aforementioned type, onto whose housing flanges is shaped an actuating lever stop flange surrounding the flap shaft. However, this solution requires complicated tools due to the considerable deformation in this flange area.
Offenlungungsschrift No. 2,819,921 also discloses a flange connection in which two solid, axially elongated rings with in each case two sets of inner inclined planes, with in each case two conical inclined planes cooperate on two oppositely directed connection pieces and consequently secure a sealing member between them. The two halves of the clamping parts are interconnected by pinning.